Particulate and fibre reinforced metal matrix composites exhibit higher strength-to-weight ratio and specific modulus than unreinforced aluminium alloys. However, the machining problem of these materials limited the use of composites in automobile, marine, chemical, precision engineering and transportation industries. Wire electrical discharge machining ( W-EDM ) is considered as an attractive way of non-conventional machining for the aluminium-based MMC materials. In this dissertation, linear cuts of particulate and fibre reinforced composite materials were conducted by W-EDM under different operating conditions. Unreinforced aluminium alloys were also taken for comparison purpose. The result shows that unreinforced 6061 aluminium alloy has the higher material removal rate than the particulate and fibre reinforced composite materials while coarse alumina particulate reinforced composite has the highest machining speed among the composite materials. The stability of machining operation relys on the setting of the process parameters and properties of materials. Metallographic examination of the machined surfaces reveals that the surface roughnesses are much worse in rough machining and for materials with large size of reinforcement phases. In addition, the W-EDM of MMC materials leads to the formation of craters and the removal mechanisms of the ceramic reinforcement phases are established.